Telecommunication systems employ a variety of cellular systems and devices to wirelessly transmit/receive voice and data signals over large geographic areas and in small confined spaces. Outdoor macro telecommunications sites typically employ, inter alia, a plurality of telecommunications antennas, e.g., sector antennas, mounted atop elevated towers/scaffolding/buildings, for the purpose of transmitting/receiving RF signals, i.e., providing cellular coverage, over a large geographic area. Such land-based antennas may communicate with and employ orbital telecommunications satellites, Distributed Antenna Systems (DAS), or other land-based telecommunications systems.
Localized telecommunications, or DAS, augment radio frequency (RF) communications, i.e., cellular coverage, provided by external/global satellite or land-based antenna systems. More specifically, a DAS provides coverage in spaces, buildings, tunnels, etc., which would otherwise block, attenuate, absorb or interfere with the RF signals/energy transmitted/received by the external/global systems. Such spaces include high-rise buildings, hotels, stadiums, universities, casinos, etc., where RF coverage is essential for uninterrupted and reliable telecom service. The objective of a Distributed Antenna System (DAS) is to provide uniform RF coverage within a defined space to optimally or selectively distribute RF energy within that space.
Land-based antennas, or Macro Antenna Systems (MAS), typically include: (i) a Base Transceiver Station (BTS) providing RF signals from local service providers, e.g., Verizon, Comcast, AT&T, etc., through a Base-Band Unit (BBU), (ii) a Remote Radio Unit (RRU) communicating RF data with the BBU and operative to augment, amplify, attenuate, and transmit RF signals received from the BBU, (iii) a plurality of telecommunication antennas each connecting to an RU, and a (iv) a tower/scaffolding/elevating structure for mounting the RRU and telecommunication antennas. The BBU is disposed in the equipment room/Base Transceiver Station (BTS) shelter and connected to the RRU via a combination of optical fiber and copper wire.
Similarly, a Distributed Antenna Systems, or DAS typically includes, at one end: (i) a plurality of Base Transfer/Transceiver Stations (BTS) providing the RF signals of each service provider, e.g., Verizon, Comcast, AT&T etc., (ii) a DAS head-end for receiving, handling, and manipulating the various RF signals of the Base Transfer/Transceiver Stations, (iii) a plurality of Remote Units (RUs) amplifying/attenuating signals received from the DAS head-end, and (iv) a telecommunications antenna connecting to each of the remote units at the other end of the DAS. Similar to a MAS, the DAS head-end connects to each of the remote units by a plurality of conductive and fiber optic cables.
A DAS may comprise a variety of system types including passive, active and hybrid systems. Passive systems employ conventional coaxial cables to distribute telecommunication signals within an internal space, active systems typically employ optic fiber cable to distribute RF signals, while hybrid systems employ a combination of the passive and active systems. passive system is generally less complex and costly to implement inasmuch as the coaxial cable employed therein is inherently capable of handling multiple carrier frequencies issued by RF service providers. On the other hand, the strength of the radio signal issued by passive system rapidly diminishes the farther the cable is from the signal source. Consequently, passive systems are not well-suited for large facilities having long/complicated cable runs, and cannot provide end-to-end cable monitoring. Active DAS, on the other hand, delivers strong and consistent signals at every node, irrespective the distance from the signal source. Furthermore, active DAS is capable of monitoring nearly all system components, e.g. the remote units, antennas, base band units, using a conventional Simple Network Management Protocol (SNMP). Finally, and perhaps most importantly, fiber optic cable used in active DAS can be run over large distances without losing signal strength. Further, fiber optic cable employed in active systems can be less expensive to install inasmuch as the cabling is lighter and easier to deploy across ceilings and in tight spaces.
DAS and MAS telecommunication systems are often protected from electrical surges, such as from lightning strikes, by Metal Oxide Varistors (MOVs) which direct potentially hazardous/damaging current away from sensitive components. More specifically, the resistance of such MOVs varies with voltage such that at low voltage the resistance blocks current flow thought the MOV and at high voltage the resistance enables current flow. In use, MOVs are typically connected, at one end, to an electrical circuit upstream of the components sought to be protected. At the other end, the MOV connects to ground, or to a structure connected to ground. During normal operation, the electrical circuit operates at a first low potential wherein the resistance of the MOV is sufficiently high to direct electrical energy into the circuit without interfering with current flow. That is, the circuit operates as if the MOV were not part of the circuit, i.e., not connected. In the event of an electrical surge or lightning strike, the increased voltage lowers the resistance across the MOV. The resistance is reduced to level to effectively connect the circuit to ground, i.e., shorting the circuit. Inasmuch as the current flow is directed to ground upstream of the components sought to be protected, the MOV prevents potentially damaging high current from adversely impacting the circuit. Once the power surge has passed, the ohmic or resistive properties of the MOV to return the circuit to its normal operation, i.e., directing current back into the operating circuit. That is, the resistance of the MOV increases to direct current to the circuit rather than to ground.
While MOVs provide a reliable source of overvoltage protection, the metal oxide materials, i.e., the zinc, cobalt, nickel e.g., used therein degrade over time and fail. That is, repeated current spikes cause the disc-shaped varistor used therein to become brittle and crack, resulting in an open circuit. This “end-of-life” or failed condition is often combated by implementing a meltable metal disc within a cavity of the MOV housing, i.e., the housing which contains the varistor disc. Upon experiencing an overvoltage condition, a high current condition causes the metal to melt, filling the gap in the varistor disc. In addition to providing the requisite overvoltage protection, the meltable metal completes another circuit issuing a signal that MOV has failed, i.e., permanently.
Detecting an end-of-life condition of an MOV is important for ensuring the efficacy of a viable surge protection system. Without end-of-life circuit monitoring, Remote Radio Units (RRUs), which are protected by such systems, can be vulnerable to a non-functioning/inoperable MOV. That is, without a periodic, and potentially premature, system of replacement, MOVs may have reached an end-of-life condition while RRUs are essentially unprotected from energy spikes/lightning strikes.
On the other hand, the use of such end-of-life circuit monitoring, typically results in RRUs being taken off-line immediately to protect expensive equipment from being damaged. Consequently, revenues associated with cellular service are lost from the time that the service is initially taken off-line to the time that it is restored. Minimally, a service call will be issued, a team of service-provider technicians deployed, an MOV removed/replaced, and a system test performed to ensure that a newly installed MOV is properly working/installed. It will be appreciated, therefore, that on the one hand, MOVs which employ meltable metal protectors become inoperable, and the RRUs vulnerable to subsequent lightning strikes. On the other hand, MOVs which simply fail, without providing a means for continued protection, take the RRUs off-line with the attendant lost revenues associated with disuse.
The foregoing background describes some, but not necessarily all, of the problems, disadvantages and challenges related to the reuse of cable connectors.